1. Field of the Invention
The present invention relates to projection display devices for projecting to screens or the like images obtained by applying light from light sources to light valves.
2. Description of the Related Art
Projection display devices are prepared for the market, which comprise light valves using liquid-crystal panels, for example, and separates white light emitted from a light source into the three primary colors of red (R), green (G) and blue (B) before modulating the three liquid-crystal panels based on an image signal. Modulated lights are subjected to color synthesis, and then projected enlargedly on a screen through a projection lens for display.
FIGS. 9-10 show a conventional projection display device. The projection display device 1 is provided with an optical unit 2, an axial flow fan 3 for cooling the optical unit 2, and an exterior cabinet or casing 4 having the optical unit 2, the axial flow fan 3, etc. mounted thereto.
The optical unit 2 is provided with a light source or lamp 21, a fly-eye lens group 22, a P-polarization/S-polarizabon (P/S) converter element 23, color separating mirrors or dichroic mirrors 25, 26, reflecting mirrors 24, 27, 28, 29, three condenser lenses 30R, 30G, 30B, three sets of light valves 35R, 35G, 35B (refer simply to as 35 in some instances) each 25 comprising an incident side deflection plate 36, liquid-crystal panels 31R, 31G, 31B and an outgoing side deflection plate 37, a cross prism or dichroic prism 32 for color synthesis, a projection lens 33, and a unit frame 34.
The P/S converter element 23 is formed out of rectangular glasses with a coated dielectric film bonded to each other by an adhesive. Moreover, on the incident side of the liquid-crystal panels 31R, 31G, 31B, the incident side deflection plates or films 36 are bonded to the condenser lenses 30R, 30G, 30B through thin glass plates, respectively. On the outgoing side of the liquid-crystal panels 31R, 31G, 31B, the deflection plates 37 are bonded to the cross prism 32 through thin glass plates, respectively.
Illumination light applied from the light source 21 is equalized by the fly-eye lens group 22, and is adjusted in the deflection direction by the P/S converter element 23, which is then separated into R, G and B by the reflecting mirrors 24, 27, 28, 29 and the color separating mirrors 25, 26.
Color lights applied to the liquid-crystal panels 31R, 31G, 31B through the condenser lenses 30R, 30G, 30B and the deflection plates 36 are modulated by an image signal, and the permeability of each is controlled through the deflection plate 37. In such a way, images formed on the liquid-crystal panels 31R, 31G, 31B are color composed by the cross prism 32, and are projected to an external screen (not shown) through the projection lens 33.
When passing through the deflection plates 36, 37, light is partly absorbed by the deflection plates to produce a temperature rise thereof. There are arranged cooling means for retraining this temperature rise, which comprise intake openings 38R, 38G, 38B arranged in the lower side of the unit frame 34 to face the three liquid-crystal panels 31R, 31G, 31B and the deflection plates 36, 37, and exhaust openings 39R, 39G, 39B arranged in the upper side of the unit frame 34 to face the intake openings 38R, 38G, 38B.
The axial flow fan 3 is disposed below the optical unit 2, i.e. roughly beneath the cross prism 32, and serves to blow cooling air on the three liquid-crystal panels 31R, 31G, 31B, the deflection plates 36, 37, etc. through the intake openings 38R, 38G, 38B arranged in the unit frame 34, which is then exhausted outside from an exhaust port, (not shown) arranged in the exterior cabinet 4 through the exhaust openings 39R, 39G, 39B.
Next, the shape or configuration of the exterior cabinet of the projection display device will be described. Referring to FIGS. 15-17, when viewing from the shape of their exterior cabinets, the projection display devices can be classified into a vertically lengthened projection display device 1001 wherein the direction of separating and synthesizing light emitted from the light source is defined as the vertical direction, and a horizontally lengthened projection display device 2001 wherein the direction of separating and synthesizing light emitted from the light source is defined as the horizontal direction. In recent years, for achieving a size and weight reduction of the device, the vertical projection display device is often used which allows a reduction in size of the optical system for separation and synthesis of light emitted from the light source, since the liquid-crystal panels are of the shorter vertical length than the horizontal length.
Referring to FIGS. 15-16, the conventional vertical projection display device 1001 is provided with an optical unit 102, an axial flow fan or cooling fan 103 for cooling the optical unit 102, and an exterior cabinet or casing 104 having the optical unit 102, the axial flow fan 103, etc. mounted thereto.
The optical unit 102 is provided with a light source or lamp 121, a fly-eye lens group 122, a P/S converter element 123, color separating mirrors or dichroic mirrors 125, 126, reflecting mirrors 124, 127, 128, 129, three condenser lenses 130R, 130G, 130B, three sets of light valves 135R, 135G, 135B (refer simply to as 135 in some instances) each comprising an incident side deflection plate 136, liquid-crystal panels 131R, 131G, 131B and an outgoing side deflection plate 137, a cross prism or dichroic prism 132 for color synthesis, a projection lens 133, and a unit frame 134.
The optical unit 2 is disposed in the vertical exterior cabinet 104 with the light source 121 side down and the light valves 135 side up.
The P/S converter element 123 is formed out of rectangular glasses with a coated dielectric film bonded to each other by an adhesive. Moreover, on the incident side of the liquid-crystal panels 131R, 131G, 131B, the incident side deflection plates or films 136 are bonded to the condenser lenses 130R, 130G, 130B through thin glass plates, respectively. On the outgoing side of the liquid-crystal panels 131R, 131G, 131B, the deflection plates 137 are bonded to the cross prism 132 through thin glass plates, respectively.
Illumination light applied from the light source 121 is equalized by the fly-eye lens group 122, and is adjusted in the deflection direction by the P/S converter element 123, which is then separated into red (R), green (G) and blue (B) by the reflecting mirrors 124, 127, 128, 129 and the color separating mirrors 125, 126.
Color lights applied to the liquid-crystal Panels 131R, 131G, 131B through the condenser lenses 130R, 130G, 130B and the deflection plates 136 are modulated by an image signal, and the permeability of each is controlled through the deflection plates 137. In such a way, images formed on the liquid-crystal panels 131R, 131G, 131B are color composed by the cross prism 132, and are projected to an external screen (not shown) through the projection lens 133.
When passing through the deflection plates 136, 137, light is partly absorbed by the deflection plates to produce a temperature rise thereof. There are arranged cooling means for retraining this temperature rise, which comprise, as shown in FIG. 16, intake openings 138R, 138G, 138B arranged in one side 134a of the unit frame 134 to face the three liquid-crystal panels 131R, 131G, 131B and the deflection plates 136, 137, and exhaust openings 139R, 139G, 139B arranged in another side 134b of the unit frame 134 to face the intake openings 138R, 138G, 138B.
The axial flow fan 103 is disposed roughly just beside the cross prism 132 of the optical unit 102, and serves to blow outside air or cooling air on the three liquid-crystal panels 131R, 131G, 131B, the deflection plates 136, 137, etc. through an intake port 104a arranged in one side of the exterior cabinet 104 and the intake openings 138R, 138G, 138B arranged in the unit frame 134, which is then exhausted outside from the exhaust openings 139R, 139G, 139B arranged in the unit frame 134 and an exhaust port 104b arranged in another side of the exterior cabinet 104.
The above projection display device 1 could contribute to an enhancement of the brightness due to a technical improvement of the light source 21, optical parts, etc. On the other hand, with an enhancement of the brightness, an improvement in cooling performance forms an essential task to restrain a temperature rise of, e.g. the deflection plates 36, 37, etc.
On the other hand, a problem arises with regard to the noise level of projection display devices when operated in conference rooms, etc. Traditionally, axial flow fans are often used having low noise level according to specification catalogs. However, the characteristic of the axial flow fans is favorable to achievement of larger air quantity, but not to achievement of larger static pressure. Therefore, in order to pass cooling air to the circumference of the cross prism 32 with greater passage resistance, etc. for further cooling, it is necessary to use an axial flow fan with larger capacity than required or apply it at high-voltage drive and high rotation, deteriorating fan noise. Moreover, filters are usually disposed at an inlet of fans to prevent adhesion of dust to optical parts, which also deteriorates the noise level.
Then, projection display devices are developed using a sirocco fan as a cooling fan. As illustrated in the characteristic drawing of static pressure vs. air quantity in FIG. 11, the sirocco fan secures greater air quantity at higher static pressure compared with the axial flow fan. Accordingly, the sirocco fan has the advantage of being capable of sending cooling air to spots with larger passage resistance in the projection display device for effective cooling. On the other hand, due to its larger noise level compared with the axial flow fan having the same capacity, an inconvenience occurs in conferences taking place with a projection display device.
Moreover, with the conventional vertical projection display device 1001, as described above, the axial flow fan 103 is disposed close to the incident side deflection plate 136, the liquid-crystal panels 131R, 131G, 131B and the outgoing side deflection plate 137 for their cooling, and the intake port 104a and the exhaust port 104b are thus arranged in the sides of the exterior cabinet 104 as shown in FIG. 16. Consequently, when using the vertical projection display device disposed on a table T or the like, an operator and an audience will directly hear noise resulting from the axial flow fan 103 through the intake port 104a and the exhaust port 104b. Therefore, the vertical projection display device 1001 produced a problem of higher noise level than that of the horizontal projection display device 2001 which allows the axial flow fan 103 to be disposed on the bottom.
It is, therefore, an object of the present invention to provide projection display devices of high cooling efficiency and low noise which allow effective cooling of optical units by cooling air and noise reduction for the whole device up to the level at which an inconvenience fails to occur in conferences, etc.
Another object of the present invention is to provide vertical projection display devices having reduced outline dimensions which allow efficient cooling of the incident side deflection plates, the liquid-crystal panels and the outgoing side deflection plates, and reduced level of noise level resulting from ventilation.
One aspect of the present invention is to provider a projection display device comprising an optical unit comprising a light source and a group of light valves, means for cooling said optical unit, said cooling means comprising a sirocco fan, a duct for bringing a cooling air produced by said sirocco fan to at least said group of light valves, and means arranged in said duct for controlling an air quantity of said cooling air, and an exterior cabinet accommodating said optical unit and said cooling means.
The sirocco fan can produce cooling air with higher, static pressure in the duct, achieving efficient cooling of spots with higher passage resistance such as a light valve, etc. The air-quantity controlling means arranged in the duct distribute cooling air with higher static pressure in the optical unit, enabling cooling in generally favorable conditions.
Another aspect of the present invention is to provide a vertical projection display device which brings cooling air of the cooling fan disposed in the lower part of the exterior cabinet to the light valves disposed in the upper part thereof. Arrangement of the cooling fan in the lower part of the exterior cabinet contributes to a reduction in noise level. Moreover, since the cooling fan is in the form of a sirocco fan which enables ventilation with higher static pressure, cooling air can be provided to the light valves disposed in the upper part of the exterior cabinet through the duct.
The inventive projection display devices are provided preferably, with the air-quantity controlling means for allowing the duct to bring cooling air to the light valves at a desired ratio.
Moreover, the inventive projection display devices including the air-quantity controlling means are provided, preferably, with the group of light valves comprising a first light valve for modulating red light, a second light valve for modulating green light, and a third light valve four modulating blue light, wherein the air-quantity controlling means bring cooling air to the first, second and third light valves at an air-quantity ratio of 1:2:3. Such a structure allows ideal ventilation to the light valves.
Preferably, the air-quantity controlling means are constructed so that air-quantity adjustment is possible from the outside of the exterior cabinet. Such a structure allows the ratio of cooling to parts of the optical unit air to be able to be controlled suitably easily from the outside.
It is preferable that the duct brings part of cooling air to the light source of the optical unit. With such a structure, cooling air with higher static pressure produced by the sirocco fan is available to cooling of the light source disposed in a different position from the light valves.
Moreover, it is preferable that the duct is arranged with a plate for adjusting the air quantity of cooling air. Such a structure allows appropriate cooling of both the light valves and the light source.
Preferably, the inventive projection display devices further comprise a fan for dispersing heat generated by the light source, the fan providing an air quantity controlled in accordance with output of the light source. Such a structure allows the fan to be controlled at an air quantity required for cooling of the light source, resulting in possible reduction in noise in accordance with output of the light source.
It is desirable that the sirocco fan provides an air quantity controlled in accordance with output of the light source.
Moreover, it is desirable that the exterior cabinet has, preferably, an exhaust port for cooling air in a surface on which a projection lens is disposed. With such a structure, when projecting images through the projection lens, cooling air after cooling each part of the optical unit can be exhausted in the direction of a screen where no person exists generally.